The flow cytometry core will isolate from the marrow of normal controls and patients with myelodysplastic disorders, cell populations enriched for pluripotent hematopoietic stem cells (PHSC), hematopoietic progenitor cells (HPC) and more differentiated precursor cells. Furthermore, subpopulations of CD34plus which are enriched for CFU-Gm (CD34plusCD64plus), BFU-E (CD34hiCD71hiCD64-) or CFU-E (CD34loCD71hiCD64-) will be isolated from the marrow of normal controls and patients with myelodysplastic disorders. This core will perform in vitro assays to detect pluripotent hematopoietic stem cells and hematopoietic progenitor cells. These assays will include long-term bone marrow cultures which detect cobblestone area forming cells and clonal assays in semisolid media to detect HPC. This core will also provide advanced training to investigators that require access to flow cytometry or assays for hematopoietic progenitor and stem cells.